Underfloor insulation across South Glamorgan
We cover 3 towns in South Glamorgan: Cardiff, Barry and Penarth.
Small measures like this are often among the cheapest per pound saved, and they suit South Glamorgan homes of every age. We check ventilation as carefully as insulation in South Glamorgan homes, because both matter for keeping a house dry.
Building Regulations in Wales
In Wales, filling an existing cavity is also notifiable building work under the Building Regulations as they apply in Wales. A registered installer normally self-certifies it through a competent person scheme; otherwise a building notice goes to your council's building control before work starts. Welsh rules can differ from England's, so the notification route is confirmed in writing on your quote.
Funding in Wales
- Warm Homes Nest offers free improvements, including insulation, to eligible low-income owner-occupiers and private renters; eligibility was widened to some households without means-tested benefits.
- Green Homes Wales has been piloting advice and interest-free loans for households above the Nest and ECO4 income thresholds.
- ECO4 runs until 31 December 2026 across Great Britain, including Wales.
Sources: Welsh Government: building work competent person schemes; CIGA: CWISC competent person scheme; Welsh Government: issues arising from cavity wall insulation installations; Welsh Government: warmer and more energy efficient homes (July 2026); GOV.UK: extending the ECO4 end date, government response.
Keeping the void ventilated
Air bricks under a suspended floor must stay clear so the timbers stay dry. Insulation goes between the joists, not across the void, and gaps at skirtings are sealed to stop draughts.
What is included
- Floor void inspection
- Insulation between joists
- Draught sealing at skirtings
- Boards relaid
Underfloor insulation prices in South Glamorgan
| Underfloor insulation guide prices | Guide price |
|---|---|
| Suspended timber floor, typical room | £795–£1,495 |
| Whole ground floor | £1,995–£3,995 |
No VAT is charged on installing insulation in homes until 31 March 2027 (then 5%). Guide ranges only: the fixed price is confirmed in writing before any work starts, and anything that could not be seen at survey is agreed with you first.
How it works in South Glamorgan:
Tell us about the property
Postcode, property type and what you would like done.
Free survey
Access, condition, existing insulation and ventilation checked.
Written result and price
What we recommend and a fixed price before any work.
Work and tidy-up
Fitted at an agreed time, with ventilation kept clear.